The present invention relates to a small-sized image pickup lens employing, an image pickup unit and a cellphone terminal equipped with the small-sized image pickup lens and the image pickup unit, employing a solid-state image sensor such as a solid-state image sensor of a CCD type or a solid-state image sensor of a CMOS type.
With high efficiency and downsizing of an image pickup unit employing a solid-state image sensor such as an image sensor of a CCD (Charge Coupled Device) type or an image sensor of a CMOS (Complementary Metal Oxide) type, a cellphone and a personal computer each being provided with the image pickup unit are spreading in recent years. In addition, a demand for further downsizing of the image pickup lens equipped on each of these image pickup units is increasing.
A two-element lens capable of being improved to be of the higher efficiency compared with a single lens is generally fit for the image pickup lens to be used for the aforesaid application, and there is known a positive-lens-preceding two-element image pickup lens wherein a positive lens is arranged to be closest to an object because of a demand for downsizing of a total lens length. The image pickup lens having the aforementioned structure is disclosed, for example, in the Japanese Patents Nos. 3,007,695 and 3,311,317.
There has been a problem in the lens of the type described in the patent official report mentioned above that an angle of view in the diagonal direction of a solid-state image sensor is as small as 52° to be slightly small as an image pickup lens to be used for a camera-fitted cellphone, although its f-number is as great as 2.0 and downsizing of the total lens length is achieved.